Multiplex sound recording and reproducing system



Nov.24, 19M. v R. J. PoMERoY 1,833,372

MULTIPLEX SOUND RECORDING AND REPRODUCING SYSTEM y Original Filed Sept.13, 1927 5 Sheets-Sheet l Inven tor Rqy .l Pomeroy :ttorrzey Nov. ,24,1931.

R. J. POMEROY 'MULTIPLEX SOUND RECORDING AND REPRODUCING SYSTEM origina1Filed sept. 15, 1927 5 sheets-sheet 2 fnvenor' RogJ Pomeroy Nov. 24,1931. R. J. PoMERoY 1,833,372

MULTIPLEX SOUND RECORDING AND REPRODUCING SYSTEM Original Filed Sept.13. 1927 5 Sheets-S1168?l 5 fnvenor Z305/ J. Pomeroy Nov. 24, 1931. RlJ. Pom-:ROY 1,833,372

` MULTIPLEX SOUND RECORDING AND REPRODUCING SYSTEM Original Filed Sept.13. 1927 5 Sheets-Sheet 4 fnl/@dor R05/ J Pomeroy Nov. 24, 1931. R. J.POMEROY 1,833,372

l l MULTIPLEX SOUND RECORDING AND REPRODUCING SYSTEM Original FiledSept. 15, 1927 5 Sheets-Sheet 5 Invenor Roy J. Pomeroy Patented Nov.1931 UNIT-lsoY STATES PATENT oFFicE ROY J. POILEROWY, OF LOS ANGELES,CALIFORNIA, ASSIGNOB OF ONE-HALF T Pm. MOUNT PUBLIX CORPORATION, YA'CORPORATION' 0F NEW YORK mecum sown momma 'AND amnopvonfte ss'rmr iApplication med September 18, 192'?, vSerial No. 219,217. Renewed April90, 1931.

This invention relates to recording and reproducing sound, and moreparticularly to recording and reproducing simultaneously and in a singlerecord, 'or concomitant records, sounds of a wide varietykl It has beenfound that a single sound record, such for instance as a single recordgroove, er a single photographic record, cannet be used for the faithfulrecording and reproductlon of sounds having Widely varyingcharacteristics, and particularly sounds that dlffer greatly in pitch.The difficulties may be vlsuahaed by considering the making andreproduction` of an ordinary phnegraph record. When the groove isinitially cut, the cutting needle is actuated by a sound operatedmechanism Aof some type or other; and it has been found very difficult,if not quite imposslble, to ac'- commodate that mechanism equally wellto sound vibrations throughout the whole pitch range of audible sound. Aneedle actuatlng mechanismthat responds accurately to sounds of a givenpitch, or throughout .a limited pitch range, is found not to respond sowell te sounds of other pitches. And even the material`in which a recordgroove-"is cut has an effect in the same direction, as it may resistlateral movement of the needle at relatively high velecity in a degreedisproportionate to its resistance to such lateral movement atrelatively lower velocity. n

Thus a single groove record sometimes falls far short of having in it anaudible representation of the large variety of sounds produced, forinstance, from an' orchestra. And furthermore, when the record comes tobe re reduced, further difficulties of the same 'nd are introduced inthe reproducing needle following the record groove, and

4o also in the sound reducing mechanism actuated by the nee le. Thesound producingl mechanism has the same shortcomings that are found inthe recording mechanism, respending best to certain pitch ranges, andless well te others; and, again, the reproducing needle, whose movementsare opposed by the forces necessary to actuate the sound producinmechanism, is in many instances prevente from following the recordgroove faithfully. The sum total result is in manyinstancesacemparatively poornal reproduction of the sounds supposed tobe reproduced. Amd although a photographic sound record uses no needlesand comprises few mechanical operating parts, the same generalshortcomings are found in that system. Typically,

film, and although light control or variation may respond with veryperfect accuracy to the pulsating current coming from the amplifieroutfit, yet in the am lifying system, and in the microphone itself), areusually found serious deficiencies in full response to a wide pitchrange. For instance, the inertia and other characteristics of themicrophone cause it to res ond best to certain pitch ranges and less weto others. While it is comparatively easy to design'and construct amicrophone which -will operate with satisfactory uniformity throughout alimited pitch range, it is cro one that will respond with satisfactoryuni ormity throughout the whole audible pitch range. Likewise in theamplifying system there are certain elements whlch cannet be givenuniform action throughout the audible itch range, and this isvparticularly true of t eV -transformers used in such amplifyin systems.Transformers have been success ully constructed which will res ond withfair uniformity throughout the middle portien of the audible range, butsuch transformers drop oif in their efficiency as both ends of theaudible pitch range are ap-V proached. Thus', such transformers, al-

practically impossible to construct a mi' though great care is taken intheir design range, it is comparatively easyto design and i constructsuch elements so thatl they will rel l spend with satisfactoryuniformity throughout a limited pitch r e, and also so Vthat outside ofthat limited pitch range, they Wili drop ed' rather sharply in their.eiiiciency.l

By making useof these characteristics ll have evolved a multi lex systemof'. sound recording and re ro uction that very e'ectively overcomes t1e diiiiculties heretofore encountered. ll do this by providing asuitable number of inde endently operating units, each unit, and t eelements thereof, being designed, constructed and operated-in suchmanner as to obtain a substantial uniformity of action t-hrou hout thelimited pitch range imposed upon t at unit. I divide the audib e itchrange into several limited ranges; then Iprovide a complete'recording orreproducing unit for acting substantially exclusively within each suchlimited pitch range. p For instance, in a recording system usingelectrical ampliers, the microphone, transformers and other elements ineach unit are designed to have satisfactory uniform response andefliciency throughout the corresponding limited pitch range. Then,because each such unit may be made com aratively poorly responsive topitches outside that range, or because in practical opera-tion each suchunitis more or less shielded from sounds to which it does not wellrespond, or because'of both those things acting in conjunction, I obtaina final sound record in which the whole range of sounds is faithfullyand accurately recorded and in which no distorted sounds are recordedbecause each recording unit has been operating only as regardsrecordation of such sounds as it is capable of recording withsubstantially perfect faithfulness. erably, each unit will make its ownseparate record. Several records may be all contained upon a sin le.record carrying element, as

upon a sing e stripof film, or upon a single P onograph disk, or may becontained upon severa different recor 'carrying elements which areoperated synchronously. It 1s' only necessary that the several recordsbe concomitant; not that they be integrated or su erimposed.

n carryin my invention into efect, it will be understoo that theabsolute efficiencies of corres onding elements in the several units, orof t ie several units, need not be the same. For instance, the absoluteeiiiciency of a microphone used for the lowest pitch ran may be quitedilerent from the absolute e c1ency of the microphone used in the unitfor another pitch range. For, as .long as lthe eiiiciency of eachmicrophone is fairly uniform throughout its own limited range, the finalrecording or reproduction may be made uniform throughout the whole rangeby yintroducing corrective factors which raise or lower the amount ofener or amplification, in one or more of the umts as av whole.

With this` preliminary discussion of the.

And, prefincassa 'invention in mind, the invention will new be,

best understood from the following detailed description ci typical formsof the system, reference for this purpose being had to the accompanyingdrawings, inwhich:

liig. l is a diagram'showing a recording system, according to myinvention, utilizing electrical amplification, and making a multiplephotographic record:

Fig. 2 is a diagram indicating a typical division 'of the audible pitchrange into Several limited ranges and showjng'eiliciency curveshereinafter explained; v

Fig. 4 is a diagram illustrating the .making of a multiple mechanicalsound record in ac.` cordance with my system;

Fig. 3 is a diagram' showing a reproduction system for the multiplerecord made by the system of Fig. 1;

Fig. 5 is a-diagram illustrating the reproduction of such a multiplerecord as shown in Fig. 4; and

Fig. 6 is a diagram illustrating'how one of my multiplex records may bemade from a sound record of ordinary type.

In Fig. 1 I indicate a plurality of microphones M, M1, M2, M3 and M4.Each of these microphones .is connected into the input glow tube to theelectrical pulsations will be understood without the necessity of anydetail description, the light emitted by each tube varying in accordancewith the pulsations.-

The. images of the glow tube may then be thrown by lenses 12 upon a'film or ilms. Typically I show all of the glow tube images being castupon a. single moving film F; rcsullting, upon development ofthe film,in a lpluralitv of photographic records R, R1, R2,

-3 and iR-i, each record corresponding to the pulsations that have beenimpressed upon the corresponding glow tube.

It will be understood that the use of a glow tube, as here shown, ismerely typicahand that the particular kind of record made by such glowtube is merel typical of several other arrangements by w ich aphotographic sound record may he made. My invention here is notconcerned with the particular kind of record, but residescharacteristically in the production andreproduction of a multiplexrecord in the manner described.

A typical amplifying system which I may use for my purposes will usuallyinvolve a number of amplifying tubes T, and transi formers L, L1, etc.'Such an alnplif ing system may involve several tubes an several iso ylargel depen amplifying unit. Various methods of circuiting may beemployed and need not here be described in detail, it being suiicient tonote that the eiliciency of such an amplifying u'nit, at varyinVvibration frequencies, is very ent upon the eiliciency of the transormers at those frequencies, Generally speaking, the amplificationeiciency of a tube is fairl uniform throu hout the audible range osound, whereas t at was nottrue of the eiciency of the transformer. Andthe first transformer in each unit, as the transformer designated L inthe drawings, is the one most important to maintain at uniformeiiicien'cy.

Fig. 2 indicates diagrammatically typical efciencies of transformers. Inthis diagram theI audible range of frequenc is shown in ordinate whileefficiency -1s in icated in abcissa- The dotted line E may be taken asshowing an eiiiciency curve for a transformer that vhas been designedand built to cover, as well as may be, the entire audible range. Fullline curves e, e1, e, e3, e* indicate ty ical eiiiciency curves of myindividual trans ormers 4L and of the several amplif ing systems A, A1,A2 etc. Each such trans ormer L, L1, etc., may be designed and built notonly as to attain as high an eicienc as practical throughout theparticular limlted pitch rano'e to which it applies, but also to obtainan e ciency asnearly uniform as may be throughout that range. 'I'hus thetransformers L, L1, etc., of the amplifying unit A are made to have auniform high eiciency for the pitch range between say 50 and 300vibrations per second; the transformers of amplifying unit A1 have thesame high uniform ericiency throughout a pitch range from 300 to 600vibrations per second, and so on, as indicated in the diagram in Fig. 2.Furthermore, each of these transformers may be so designed andconstructed that its efficiency may dro oi rather sharply at or near thelimitso the corresponding pitch range, so that each transformer,although fully responsive to vibrations within its corresponding pitchrangeA will be com aratively unresponsive to vibrationsoutsi e itscorresponding pitch range. Such a condition is indicated by theincipient drops at the ends of each of the curves e, e1 etc. And 'what Isay of the characteristics o the transformer of the `individualamplifying units, may also be true of the characteristics for themicrophones of each of these units, and ofeach unit asa whole;each'microphone being designed and constructed so as to have a uniformhigh eiciency within its coresponding pitchr range; and may also have adecided efliciency drop at or near the limits of its pitch range. Thefactors which control design of such elements, 'such as transformers ormicrophones, to attain uniform high efficiency, within a limited range,are known to the art and need no speciic setting out here.

But. when all Isuch elements have been so designed as to attain thecharacteristics desired 1n my system, it will in man cases be found thatthe absolute efficiency .o the elements of one unitl differs from theeiliciency of the corresponding velements of another unit; landV that,correspondingly, the over-all eiliciency of one com letefunlt, includingits microphone m'ay quite different from the overall eiiiciency ofanother such unit. These absolute differences in eiliciencies, however,may be easily eachumt as a whole for instance, by properly adJusting andcontrollin the ratio of amplication that takes place 1n one or more ofthe ampli ing tubes. B such adjustment and contro the .several e ciencycurves e, e1, etc., may be made to lie very straight line across the diaam of l wlthla corresponding equality in efficiency of recordation ofthe several classes of sounds which are being handled by the severalam-I plifying units.

To explain the use of my system for sound recording, let the recordingof an orchestra be consldered. In an orchestral production lthere aresounds ranging usuall substantially to both limits of audibilitreferably in recording orchestral music t e several micronearl in a Fig.2

phones M, M1, etc., will be placed each in the most advantageousposition for taking the class of sounds to which its transmitting andamplifying unit is best adapted.

The classification of the microphones and the units being on the basisof pitch, it may be advantageous to some degree to arrange theinstruments of an orchestra more or less in accord with their averagepitch ranges; so that those of lowest pitch ma be effectively groupednear microphone M those of the next pitch range being grouped nearmicrophone M1, and so on. Also, it may be desirable partially to shieldthe several microphones against sounds from instruments out of theirrespective pitch ranges; but such shielding cannot be carried too far,especially if the several units are very little responsive to pitchesout of their respective selected pitch ranges, as thereby characteristicovertonesl of instruments might be too much lost inthe record. v v InFig. 3 I show a system of reproduction corresponding to the recordmaking system of Fi 1. Here the record lm F is illustrate passin beforea number of sensitive elements S, 1, S1, Ss, S1, to intercept light fromsuitable illuminants I falling upon the several records and passingthrough the records to affect the sensitive elements S, etc.

the same as those shown in Fig. 1. For simplicity of illustration, theamplifying units, except unit A, are merely indicated in block on t ediagram. The output circuits 10 of these several amplifying units thengo,re spectively, to the lspeakers H, H1, i 2. The same controllingconditions of design and construction. are observed in the reproducingunits as in the record makingunits; and the same general results areachieved as before described. dust as inthe record producing system allof the various sounds, regardless of their wide pitch range. are fullyand faithfully recorded; 'here in the re roducing system all such soundsare faith' ully and fully reproduced with a uniformity of resultsextending throughout the range of sounds.

In addition to the selective arrangements hereinbefore described, or inpartial or substantially complete substitution therefor, otherarrangements may he used in the system. For instance, around thesecondary of the first transformer L an adjustable tuning resistance Rmay be used; or around the secondary .of the transformer' L1 anadjustable tuning condenser C may be used. By proper adjustment of. suchelements the responsive range of an amplifying unit may be more or lessconcentrated within the selected limited pitch range, and theefliciency, and uniformity of efficiency, within that limited pitchrange may be increased and fixed. And it may be well here to note that,although the efficiency of any one unitmay not be quite uniformthroughout its corresponding limited pitch range, that fact is not onewhich negatives the general results attained by my system. A slight droploff in efficiency toward the ends of the limited range is not of sogreat disadvantage as thev shortcomings which my system is intended toovercome. And, furthermore at points near the limits of the severalranges each unit is to a'certain extent reinforced in its action by theunit or units of the pitch :anges adjacent. As indicated by the curvesin Fig. 2, although, outside its own pit/ch range, each unit may dropoff rather sharply in efficiency, it Will` unless.

completely shielded from sounds except in its own pitch range, addsomewhat to the action of an adjacent unit and thus maintain the generaluniformity of total results.

Fig. 4 shows the same genera-l arrangement for record production asshown in Fig. 1 except tha't here the several output circuits 10 fromthe amplifying units, go to electromagnetic devices 20, one for eachindividual unit, these devices vibrating the several record cuttingneedles 21, to cut'the record grooves G, G1, G2. etc. Also, in thiscase, I 'show each record'groove, each record roper, bein made onaseparate record disk Althoug 1 the several record grooves inl thisarrangement could of course be cut alongside each other on a singlerecord blank, it might not be possible in such an arrangement to obtainscribed.

incedere a suitable lengt-li'. of record on a single can f l rier.Figetherefore illustrates not only the application of im` system to a,mechanical record, but also i lustrates the arrangement of the severalrecords on separate carriers.

And in a system such as shown in Fig. d, the

electromagnetic devices 20, may also preferably be designed andconstructed so as to respond, like the other lements of the several"units, with uniform high ecicncy through- Iout their respective pitchranges; and they may furthermoreV .be designed and constructed so as tobe relatively non-responsive to sounds outside v their respective pitchranges. The details of such designing are known and need no extendedexposition here.

In Fig. 5 I show a system of reproduction corresponding to the system ofrecord mak- V ing at Fig. 4. Here the several record blanks 3. The finalresults are, in general, the same as resultsbefore described.

In Fig. 6 I indicate how my system maybe used for the production of`multiplex records from a single ordinary record. As I have describedbefore, a part of the difficulties overcome by this invention reside inthe reproduction of rcords. In other words, a

well madel single'sound record', although it has not the perfection ofmy multiplex record,

still has in it such sound representations that,

if they can -be faithfully and fully reproduced, will give improvedresults. This I can do by applying my multiplex system to such a record.For instance, in Fig. 6 let Bs represent an ordinary phonograph recordwith its single soundoove G5. The mag# netic pick-u 25a Will 1n thiscase be one that will respon( as well as possible throughout the wholeaudible range.` From this mag- L netic pick-up a circuit 30 with branchcircuits 31 may lead to the several initial transformers L oftheamplifying units A, A1, A, etc., which maybe the same asbeforedescribed in all of their characteristics. Then the outputcircuits l of several amplifying units may goeither to microphones, asin Figs. 3 and 5, or they may go to electromagnetic recordin devices 20operated to cut individual recor grooves G, G1, etc., in severaldifferent record blanks B; in other words, the output circuits 1() maygo to any kind of sound wave producing mechanism. In one case, the finalsounds are immediately produced; in the other case the sound waves aretranscribed upon individual records which may then bereproduced in themanners hereinbefore del lao'

